A conventionally known variable valve operating device that is disclosed, for instance, by Japanese Patent Laid-open No. 2003-239712 mechanically changes the valve lift amount and valve timing in accordance with the operating state of an engine. In the variable valve operating device (hereinafter referred to as the conventional technology) described in Japanese Patent Laid-open No. 2003-239712, a control arm is fastened to a control shaft, which is positioned in parallel with a camshaft. One end of a follower is installed over the control arm and allowed to swing freely. A swing cam is installed over the control shaft and allowed to swing freely, and a rocker arm is pressed against a surface of the swing cam. A first roller and a second roller, which can rotate independently of each other, are concentrically installed over the follower. The first roller is in contact with a valve cam of the camshaft, whereas the second roller is in contact with a flat surface (contact surface) that is formed opposite the swing cam surface of the swing cam.
When the control shaft rotates to vary the rotation position of the control arm in a situation where the above configuration is employed, the follower becomes displaced to change the distance between the control shaft and the contact position between the swing cam and the second roller, thereby changing the lift amount of the valve. Further, when the circumferential position of the valve cam, which comes into contact with the first roller at the same rotation position of the camshaft, varies, the valve timing simultaneously changes. In other words, the conventional technology described in Japanese Patent Laid-open No. 2003-239712 is capable of simultaneously changing the valve's lift amount and valve timing by using a motor to control the rotation position of the control shaft.
Including the above-mentioned document, the applicant is aware of the following documents as a related art of the present invention.
[Patent Document 1]
Japanese Patent Laid-open No. 2003-239712
[Patent Document 2]
Japanese Patent Laid-open No. 2002-371816
[Patent Document 3]
Japanese Patent Laid-open No. Hei7-63023
[Patent Document 4]
Japanese Patent Laid-open No. 2004-108302